The present invention relates to a device for measuring properties of a textile product disposed within a measuring gap.
One example of a textile product measuring device of this kind is disclosed in DE-A-36 21 324. In this device, two capacitors, a measuring capacitor and a compensation capacitor, are provided, both of which are connected to their own oscillator circuit and have their own gap between the electrodes or capacitor boards. The textile product is moved through the gap of the measuring capacitor, to measure the properties of interest. The gap of the measuring capacitor and the gap of the compensation capacitor are both provided with a device with which the width of the gap can be set. This device is designed in such a way that both gaps open or close to the same extent, so that the device can be set to different dimensions of textile products.
One limitation of this known device arises from the fact that the device for altering the distance between the boards of the two capacitors is very complicated and heavy. This device must operate sufficiently accurately to convert changes in the gap width on the measuring capacitor into a change in the gap width on the compensation capacitor as accurately as possible. This device cannot compensate for mechanical changes to the gap width which may take place inadvertently during the measurement. This also applies to other changes in the circumstances in the two gaps which do not take place simultaneously at both gaps, such as humidity changes in the measuring gap which are attributable to damp yarn and occur on a localized basis only.
A capacitive measuring head for yarn is disclosed in CH 551 007, in which a compensation capacitor is provided symmetrically and hence on each side of a measuring capacitor. The electrodes are much wider than the yarn so as to generate as uniform a field as possible in the measuring capacitor. To prevent interference fields, the connections or supply conductors to the electrodes of the measuring capacitor and the compensation capacitor are located in or behind the carrier material which holds the electrodes.
A disadvantage of this latter arrangement results from the fact that a relatively large area in the measuring head, and hence also in the measuring gap, is occupied by electrodes. In addition, the supply conductors to the electrodes, which are led towards and away from the electrodes in a direction perpendicular thereto, produce a structure which requires a great deal of space overall and is difficult to produce.